Embossing hardboard



J. BUCKLEY ET Al.

EMBOSSING HARDBOARD Filed July 20, 1953 INVEN TOR. JOHN L. bZ/C'KAEVATTOPA/EVS Unite States Patent 2,863,168 EMBOSSING HARDBOARD John L.Buckley and Lawrence G. Buckley, Seattle, Wash. Application July 20,1953, Serial No. 368,854 9' Claims. c1. 18-10) For many years variousmaterials have been embossed for many and varied purposes. Thin,flexible materials, such as artificial leather, wall paper, or doilies,have been embossed in relief from one surface through to the othersurface; solid pieces of wooden molding, plain or covered with aflexible surfacing material, have been embossed on a single surface;more recently rigid, cut-to-size wall panels have been embossed on onesurface, principally when made of plywood. The present invention relatesprimarily to such wall panels or panels of similar nature, but to suchpanels made of hardboard, as hereinafter defined, and to the embossmentthereof on one surface.

It is self-evident that thin, flexible materials, whether or notlaminated, are readily embossed through and through, but that theproblems arising in their embossment are quite different from theproblems which arise in the embossment on a single surface of heavy,stiff, thick, resistant, materials, such assolidwood, plywood, orhardboard. Also, as will appear more fully hereinafter, the problemsinvolved in the embossment of solid wooden pieces, or of plywood formedof thin laminations of wood veneer, are rather different from theproblems involved in the embossment of hardboard. The solid wood isdifficult to depress, and so in practice the embossment thereof can onlybe in narrow Zones, or in somewhat isolated, areas, due to thedifficulty of applying sufficient pressure and heat without crushing andruining the piece, in the embossed area. Also, in plywood there is atendency for the pressure employed, particularly if all-over embossmentof the area of a large panel is required, to splinter out the back sideof the panel, for such embossment can only be done by passing the panelbetween two rollers, an embossing roller and a backing roller,betweenwhich the pressure is heavily concentrated along a very narrowtraveling Zone in very thin face plies, and the tendency is to crush andbreak loose the grain layers and to cause grain separation andsplintering in at least the underface of the plywood panel. Theapplication of Lawrence G. Buckley, one of the inventors herein, SerialNo. 143,932, filed February 13,1950, and now abandoned, deals with thislatter problem.

Aside from these technical difficulties of embossment of plywood panels,whereas plywood for many years was plentifully available in good gradesand at reasonable prices, and so the embossed plywood was readilyavailable and in good demand, more recently even veneer faces have beenpatched and of lower grade, mostly unsuitable for embossment, and so theunavailability of sound, first grade veneer, whether for plain orembossed panels (and only such grades can be used in embossing) hasadded to ,the cost. of such panels of embossed ply-f wood, and indeed.hasincreasedthe cost and reduced the availability of high grade plywoodfor any purpose, wherefore, it hasbeenattempted recently to embosshardboard, ,which has tended recently toreplaceplywood as a,buildingmaterial. Hardboard in the sense thus used iii is a built-upfiberboard of substantially density, strength and rigidity, in which thewood fibers are felted and more or less compressed together, in randomdisposition and with little residual compressibility, all bondedtogether by a binder usually consisting of or incorporating athermosetting resin. Such hardboard is usually manu-. factured byforming individual panels in the fiat in a mold, sometimes by a coldprocess, but usually by a hot press process, the heat and moderatepressure being used to effect thermosetting of the resinous binder.

Attempts have been made heretofore to emboss various hardboard panels inthe process of their manufacture, and particularly, in the hot pressprocess, in the final pressing stage of the manufactured form. To acertain degree such embossment has been successful, but with very greatlimitations. eight feet, or more, in size. The pressure required in thishot press completion of a hardboard panel is of a value far'less perunit area than is required to emboss other than the very shallowest ofpatterns, and then usually only in a depressed area limited to a smallpercentage of the total surface area. In consequence all embossment ofhardboard in the hot press, or in any analogous all-over fiatembossment, has resulted only in a very shallow pattern of limited areaor extent. Such patterns can consist primarily only of depressed narrowlines, rather than an over-all embossed pattern. These considerationslimit the pattern to one which cannot be painted, for paint will almostobliterate, the shallow pattern and fill the narrow depressed lines.This is a very serious drawback, inasmuch as the hardboard in itsnatural color has a somewhat unattractive or unfinished appearance whichmakes painting very desirable. Due to these limitations of embossedhardboard as heretofore embossed, the product has been satisfactory onlyas a novelty rather than as an overall panel for finishing walls.

Roller embossing of hardboard, by which. pressure can be concentrated ina narrow, traveling pressure zone, has been attempted heretofore, butemployment of the processes normal to the roller embossment of plywoodpanels, namely the passing of the panel between a heated patternedembossing roller and a backing roller, have not been wholly successful.The pattern can only thus be deeply impressed into the surface of thehardboard, but the natural resilient characteristics of the feltedfibers of a hardboard panel which has been completely formed and setwhen thus embossed, including its lack of a crushable wood cells and ofgrain structure, cause the depressions to spring back, in contrast tothe crushing effect on the wood cells in the thin veneer facelaminations in plywood, and this, plus the obliterating or obscuringeffect which is inherent in the somewhat mottled appearance of thesurface of a hardboard panel, tends to eliminate to a high degree thefine details of roller embossment of finished hardboard panels.

In the attempt to eliminate these difiiculties, we have heretoforeproposed to effect embossment of a hardboard panel at the time of, orsubsequent to, the application of a paper facing to the embossed surfaceof the panel, such process being disclosed in our application Serial No.298,774 filed July 14, 1952, now abandoned. Embossing performedaccording to the process therein disclosed results in a retention by theresin-impregnated paper facing, of the embossed pattern, even though thehardboard itself does not receive and retain the pattern to any higherdegree than if the paper facing were'not' present. In other words, thepaper facing is more readily receptive of, and retentive of, theembossed pattern, than the hardboard, and-thereby the lack of retentionof thepattern by thefibers and upon the surface of the hard-" boarditself is overlooked. The paper facing being of Patented Dec. 9, 1958"Such panels are usually four feet. by

more uniform appearance per se, its presence also eliminates theobliterating effect of the surface appearance of the hardboard itself.The hardboard itself, embossed according to the process of our saidapplication, does not per se retain the fine details of the embossedpattern, and without the paper facing such a panel would be' nodifferent than. an unfaced hardboard panel embossed by the rollermethod. The application of the paper facing adds an element of cost, andsince the paper is subject to damage, it is still desirable to. providea 1 method of embossing a persisting and adequately deep and sharpover-all pattern directly upon a hardboard panel, andv particularly ofembossing a pattern such as is of an over-all extent, including groovesof random width, dcpth and shape, and of appreciable depth wheredesired, and of having the hardboard itself retain that embossed patternso that it may be painted or otherwise finished, and so that the patternso embossed will not be obscured or obliterated by the painting. Theprovision of a. method and of apparatus. to effect that desired end isthe principal object of this invention.

One important drawback of hardboard as a wall panel is that it expandsrather appreciably with absorption of moisture, to any extent up to A3inch across the width of-afour foot panel. While this drawback is notpeculiar to hardboard panels alone, it is present in hardboard panelsand means that such panels must be applied to a wall with rather wideand unsightly gaps between them, so, as to accommodate subsequentexpansion, or that if twofsuch panels are placed in close edge-abuttingrelationship such gaps 'will develop if the panels shrink, or will causebuckling of the panels later if the panels swell with access ofmoisture. In view of such gaps and the necessity to camouflage them, orto reduce their obviousness in the wall, it is highly desirable that anypattern embossed on hardboard wall panels should be of considerabledepth, and in the form of straight line or parallel ridges and groovesof random width, depth and shape, so that the gaps will blend into theembossed pattern and tend to obscure the presence of the gaps. This,then, is another reason for desiring to emboss an overall pattern ofthis type on hardboard panels, and for reasons given above, it has beenimpossible to do this by any flat pressing method, and it has beenimpossible to do it heretofore in such a way as to obtain and retain thedepth and sharpness of the pattern even when embossed by rollers. It isan object of this invention to provide a method and apparatus to carryout the same whereby a pattern of this nature and for such a purposecanbe: applied practically and economically to a finished hardboardpanel, so that such panels may be used as a wall surface and Will hidethe scams or gaps between panels.

The present invention concerns the method by which roller, embossm-entof a hardboard panel of the nature and having the characteristicsindicated above may be accomplished, and concerns also the apparatus bywhich such a method is carried out.

In the accompanying drawings the invention is illustrated in connectionwith two forms'of the apparatus, anclthe several variations possible inthe method will be morefully brought out hereinafter.

Figure 1 is a longitudinal sectional view, on a vertical plane, througha complete machine arranged for carrying out the method according to oneproposedprocedure, and Figure 2 is a similar view showing the apparatusarranged for carrying out the method according to a somewhat modifiedprocedure.

In the drawings P1 represents a panel which is substantially completelyembossed and-which is emerging from between the embossing rollers. P2indicates a panel which, is' in process of being preliminarily treatedand which is aboutto pass between the embossing rollers, and P3designates a panel which is about to be fed into the machine, and uponwhich the processing is about to begin. Each such hardboard panel (beingusually of a size four feet by eight feet, or if not pretrimmed,slightly wider and longer than that) is fed face down from a feed table9 between two feed rolls 81 and 82. The roll 81 is preferably driven, asby drive means indicated at 80, from a motor 8, and the roll 82 is urgedtoward the roll 81 but held from it by suitable adjustable pressuremeans indicated diagrammatically at 83. The motor 8 also drives theembossing roller 1 at the exit end of the machine, the peripheral rateof these two rollers 1 and 81 being kept the same through the respectivedrive means to them. A backing roller 10 is located above the patternedembossing roller 1, and is pressed toward the latter with heavy pressure(perhaps 200,000 pounds across a four foot panel), by pressure meanstypified at 11. The feed rolls 81, 82 are spaced longitudinally from theembossing roller 1 and its companion backing roller 10 by a distanceslightly less than the length of the panel, although they could be morewidely spaced if desired, in which latter case the feed of a given panelwould be by pushing of a following paneluntil the' leading panel comesinto the nip between the rollers 1 and 10.

Preferably the rolls 81, 82 are housed within a casing 2, which definesagenerally elongated oven space 20,= wherein are located horizontalguide channels 21 out standing from the sides of the housing to receiveand guide the side edges of the panels, as they pass through the oven.Inasmuch as the panels such as P2 are thus of the full width of theoven, they in turn subdivide the oven space into a lower compartment 22and an upper compartment 23, with one side or portion of eachcompartment being defined by and coincidingwith the planar surfaces ofthe panel. The patterned embossing roller, whereon the pattern isengraved or cut preferably as a series of parallel ridges and grooves'ofrandom shape, width and depth, is preferably located in the lower compartment 2..

Means are provided to heat the patterned emb'oss'in'g' roller 1, and tothis end a conduit or header 4' for a cornbustible gas may be providedwith a number of longitudinally spaced apertures constituting burningjets, whereby the pipe 4 constitutes a bank of burners playing upon theunder side of the roller 1 to heat it to the desired temperature. Such abank of burners is preferably housed within the oven space 20 at theexit end thereof, so that the hot gases fill the lower chamber 22, andserve to-heat the under side of the panels P2 which divide the oven,this under side being the'surface which is to be embossed. Such gasesmay exit at the far or entrance end of the oven, and in this mannertheyprogressively heat the'panel, so that its temperature is highest at'the point where'it enters the nip between the rollers land 10.

In. addition to heating the panel, one of the essential features of. theprocess is that the under surface, at least, of the panel must bemoistened at about the time that the panel enters the oven, so that themoistened surface isheated, and the moisture is caused by the beat topenetrate somewhat deeply into the under surface of the panel. In orderto achieve these results a moistening roller 3 is located in thevicinity'of the entrance 24 to the oven, preferably just within thatentrance or just past the feed rolls 81, 82. This moistening roller maybe felt-covered, and dips into a trough 31 which is kept filled with aliquid 30, which is absorbed by'the periphery of the roller 3 and isapplied by the latter to the under surface of'the panel P2 as the panelis passing over the roller. A hold-down roller 32 may be employed abovethe panel and in conjunction with the moistening roller, to insure evenapplication of moisture to the panels under surface. Preferably theserollers 3, 32am not driven rollers.

It may be that-the moistening conditions the cells of the wood particlesincorporated in the hardboard, much as a steamed wooden rib or plank canbe permanently bent or deformed in boat-building, but this is notadvanced as the explanation, merely as a possible theory. Again, it maybe that the moistening swells the wood fibers, making them less denseand more susceptible to deformation.

The liquid at 30 may be no more than water, or a like moistening liquid,but preferably it contains a synthetic resin dissolved in the water.Preferably such resin is of the thermoplastic, thermosetting type. Whilethe concentration of the solution is not critical, best results havebeen obtained from a solution of 20% of such synthetic resin in water.Proportions from to 25% have been found reasonably satisfactory.

Such a resin solution, applied in the manner indicated to the under sideof a panel adjacent the entrance to the oven, is caused to be heated andto penetrate this under surface of the panel by the heat which isapplied to the under surface of the panel during its passage through theoven. In this passage, which will require approximately forty-fiveseconds to one minute, the resin, which penetrates the panels undersurface, plasticizes the surface to an adequate depth by the time thepanel reaches the embossing roller 1. It has by then achieved atemperature preferably of approximately 325 F., during the passage ofthe panel through the oven. The embossing roller 1 is preferably at thesame temperature of 325 F., so that the embossing roller may deeplyimpress the plasticized under surface of the panel, and the plastic,which has penetrated this surface of the panel, is in a thermosettingcondition when it issues from between the embossing rolls onto theoifbearing table 7. A hold-down guide 70 cooperates with the offbearingtable 7 to hold the panel down, and the better to prevent it fromcurling as it issues in a some what thermoplastic or pliable conditionand before it has fully set. The panel upon issuing cools down fairlyrapidly, and can be readily handled in removing it from the oifbearingtable.

If the panel has not previously been trimmed to width, trim saws 6,placed at proper spacing at its opposite edges and supported from theoffbearing table 7, will effect the edge-trimming of the panel, and itis thus assured that the trimmed edges will be precisely parallel to theridges and grooves of the embossed pattern.

As has been indicated above, the oven may be longer, for example sixteenfeet instead of eight feet approximately, but if longer the feed-throughrate should be increased correspondingly, so that the panel is subjectedin any event to the effect of heat and moisture for only about the sametime, that is, approximately one minute or less.

The panel, when finally cooled, has the resin contained in its embossedsurface thermoset by the heat and pressure of the embossing roll,leaving a hard, moistureresistant embossed surface.

The heat applied to the panel and the heat applied to the embossingroller, either or both, may be other than the heated gas, the gas ofcombustion described above. For example, in Figure 2 a steam pipe isrepresented at 5, with a control valve at 50, leading to the interior ofthe embossing roller 1 through its journal at one end, and this steam,after heating the embossing roller, issues through the opposite journaland into a discharge pipe 52, which preferably is directed within thelower portion 22 of the oven, where this steam, passing out at theentrance 24 opposite the embossing roller, heats the under side of thepanel and moistens it in passing.

The embossing roller might be heated, by means common in the art andother than those specifically described above, for example, by embeddedelectrical heating elements. In such a case other means to heat theunder side of the panel as it passes through the oven would bedesirable, and could be supplied by such means as infrared lamps playingupon the under side of the panel,

in its passage, as is common for heating in various arts.

We claim as our invention:

l. A method for embossing a single surface of a thick, dense, andsubstantially rigid panel of hardboard such as contains a previously setbinder, which method comprises continuously advancing successive panelsendwise in a single plane, applying a liquid thermosetting resinousmoistening and penetrating agent to the surface to be embossed, passingthe panel, at a distance in its path from the liquid-applying station,between a patterned embossing roller applied to the moistened surface,and a paired backing roller applied to its opposite surface therebyembossing said moistened surface, continuously subjecting the surface tobe embossed, from a point in the vicinity of the liquid-applying stationto a point in the vicinity of the embossing station, to temperatureswhch progressively increase as. any. given point on that surfaceapproaches the embossing station, to effect penetration of the panel bythe applied liquid, and cooling the panels embossed surface promptlyafter it passes the embossing station, to set the applied resinousmoistening agent.

2. A method as in claim 1, including continuously heating the embossingroller by playing thereon a bank of flames, and conducting the gases ofcombustion from said flames across the moistened surface of the panel,to the vicinity of the liquid-applying station, as the heating mediumfor such surface.

3. A process of embossing a sharply detailed overall pattern upon asingle planar surface of a hardboard panel of the character described,which comprises moistening the surface of the hardboard panel which isto be embossed with a water solution of a thermosetting resin, andheating the so-moistened surface to a temperature to soften such surfaceand to cause the mostening agent to penetrate at least to the depth ofthe pattern to be applied, and to soften the surface, but insufiicientto set the resin; passing the panel while so heated and moistenedbetween a patterned roller applied to the moistened surface and abacking roller'applied to its opposite surface, the pressure between thetwo rollers being sufficient to impress the pattern deeply into thesoftened surface of the panel, and the temperature of thevembossingroller being sufficient to set the resin in the moistened surface, forretention of the pattern impressed.

4. A process as set forth in claim 3, wherein the heat ing of the panelssurface is accomplished by directing a hot gas onto such surface duringits advance towards the embossing roller.

5. A process as set forth in claim 4, wherein the hot gas is the productof combustion of a gas.

6. A process as set forth in claim 3, wherein the heating and embossingis accomplished in a period of time not exceeding about one minute.

7. A process as set forth in claim 4, wherein the heating and embossingis accomplished in a period not exceeding about one minute.

8. Mechanism for embossing a single surface of a thick, dense andsubstantially rigid panel of hardboard, such as contains a previouslyset binder, said mechanism comprising means to advance successive panelsendwise in a single and generally horizontal plane, means defining anelongated compartment having a portion coinciding with said plane, meanslocated adjacent one end of said compartment to apply, to the planarsurface of said panel adjacent said compartment, a liquid resinousmoistening and penetrating agent, a patterned embossing roller and apaired opposed backing roller having a nip therebetween, locatedadjacent the other end of said compartment in positions to engage thesurfaces of the passing panel, at least a portion of said embossingroller adjacent the nip of said rollers being within said compartment,and means to supply a gaseous heating medium within the compartment, ata location adjacent the embossing roller and for exit of said medium atsaid one end of the compartment, to heat slich s'nrfa'c'e' adjacent saicl'c'cirflpai'tm'nf td' p'rdgress'ivelyhigher temper'atures' as itapproaches theembossing roller, and to facilitate p'ene tfa'tidn l'iythliquid'agent.

M'eeh'afnisIiias" in claim 8, wherein the embossing roller is Idcat'ed'Completely within the compartment, and including a bank of burnersextending lengthwise of and directed n'pbn the embossing roller to heatthe same, whef'e'by' the" gases of combustion from said burnersc'o'n's'titu'te' the g'aSeous heating medium, and exit from thec'dmpartmenf through said one end thereof, and one shrfakie 'of'thep'anel issuc'cessijvely moistened with the liqiiid'r'esi'ndu's' agent,heated and embossed.

Refei'e'nc'esCit'ed in the file ofthis patent UNITED STATES PATENTS 8Fischer Aug. 13, Ldngren OCT. 23;. Bl o'n'son Apr; 1 8, Zinser Ocjt. 8,Jenett Feb; 11', France Oct." 29 Smith Jan; 14, Lundstrom Sept. 11,Va'rner Jan. 1, Getchell' Sept. 9, Collins' Oct; 13; Brown Nov. 22,

